Looking at some circles

Some thoughts around the class of plane figures defined as all points equidistant from a fixed point. Some aspects of this might include stone circles and water cults, concentric circles and temporary autonomous zones, the peradam, white holes, knots, magic, the sun, Venn diagrams, Bruno, Borges, Emerson, Euclid, the letter O. See also: spheres, esp. those whose centers are everywhere, but whose circumferences are nowhere. And lemons.